CVE-2016-3071 in Libreswan
Summary
by MITRE
Libreswan 3.16 might allow remote attackers to cause a denial of service (daemon restart) via an IKEv2 aes_xcbc transform.
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Analysis
by VulDB Data Team • 07/25/2022
The vulnerability identified as CVE-2016-3071 affects Libreswan version 3.16 and represents a significant denial of service weakness within the Internet Key Exchange version 2 protocol implementation. This flaw specifically manifests when processing IKEv2 packets containing an aes_xcbc transform, which is a cryptographic transform used for authentication purposes in IPsec connections. The issue stems from insufficient input validation and error handling mechanisms within the daemon process that manages IKEv2 negotiations.
The technical exploitation of this vulnerability occurs when a remote attacker crafts and sends specially malformed IKEv2 packets containing the aes_xcbc transform to a vulnerable Libreswan daemon. The daemon fails to properly handle this specific transform type, leading to an unexpected termination or restart of the IKE daemon service. This behavior creates a persistent denial of service condition where legitimate users cannot establish secure IPsec connections until the daemon is manually restarted or the system is rebooted.
From an operational impact perspective, this vulnerability poses substantial risk to network security infrastructure that relies on Libreswan for IPsec connectivity. The daemon restart caused by this flaw can disrupt ongoing secure communications, potentially affecting critical business operations that depend on encrypted network connections. Network administrators may experience unexpected service interruptions and increased maintenance overhead due to the need for manual intervention to restore service availability.
The vulnerability aligns with CWE-248, which addresses "Uncaught Exception" conditions in software implementations. This classification indicates that the underlying issue involves an unhandled exception or error condition that causes the application to terminate unexpectedly rather than gracefully handling the malformed input. The flaw also demonstrates characteristics consistent with ATT&CK technique T1499.004, which involves network disruption through service availability attacks. The attacker can leverage this vulnerability to systematically disrupt network connectivity services without requiring elevated privileges or complex exploitation techniques.
Mitigation strategies should prioritize immediate patching of affected Libreswan installations to version 3.17 or later, which contains the necessary code modifications to properly handle the aes_xcbc transform. Network administrators should also implement monitoring solutions to detect unusual daemon restart patterns that may indicate exploitation attempts. Additionally, configuring firewall rules to limit IKEv2 traffic from trusted sources only can reduce the attack surface, while implementing intrusion detection systems can help identify and alert on suspicious packet patterns containing the vulnerable transform. Organizations should also maintain regular security updates and vulnerability assessments to prevent similar issues from emerging in other network security components.